Portable telephone systems such as cellular phones have extensively diffused among people because of the convenience of such system that the carrier of the system can be paged wherever he is, and he can call up his partner from anywhere. Particularly, because of recent improvements of cellular phones and infrastructures of cellular phone systems, cellular phones have functionally evolved beyond mere telephonic devices and have become versatile portable information apparatuses having information processing functions to deal with e-mail and retrieve information.
These portable information apparatuses e.g. cellular phones are configured to transmit electromagnetic waves not only for communication with a relay station (hereinafter referred to as base station) to talk with partners but also for period registration of their current locations at the base station so that the apparatuses can receive telephone calls and e-mail.
As a result of dissemination of such portable information apparatuses, strong electromagnetic waves are emitted everywhere for communications, thereby posing serious problems to devices such as cardiac pace-makers that can fail under strong ambient electromagnetic waves.
A countermeasure for such situations is to have the portable information apparatuses turned off, as in actuality requested to do so in public facilities. However, the portable information apparatuses e.g. cellular phones have versatile information processing functions to deal with e-mail and to retrieve information. They are suited to read information received and/or prepare e-mail while waiting for receipt of a message. Consequently, it is difficult to resort to the sense of morality of the carriers to turn off the portable information apparatuses.